# A worker at a petrol station notices a small spark as they reach for the fuel nozzle. Explain why static charge can build up on the worker's body and why this sparking is dangerous at a petrol station. You should also explain how earthing the fuel pump reduces this risk.

> OCR A-Level Physics B: Advancing Physics (H557) — 3.2 Forces in action · Explain · 5 marks

> Petrol stations require all fuel pumps to be earthed. Workers are advised to touch a metal surface before handling fuel nozzles.

## Mark scheme (5 marks)

1. Static charge builds up on the worker because electrons are transferred when clothing/shoes rub against surfaces (e.g. seat, floor)
2. The worker's body becomes charged because the charge cannot flow away — the worker is an insulator (or is not earthed)
3. Sparking occurs when enough charge has built up and electrons jump through the air between the worker and the nozzle to balance the charges
4. The spark is dangerous because it can ignite petrol vapour, causing a fire or explosion
5. Earthing provides a low resistance path for electrons to flow away from the pump to the ground, preventing charge from building up / removing excess charge safely

## Key terms

- [static charge](https://www.gradenine.co.uk/glossary/static-charge)
- [sparking](https://www.gradenine.co.uk/glossary/sparking)
- [earthing](https://www.gradenine.co.uk/glossary/earthing)

## Related

- [Revision notes for OCR A-Level Physics B: Advancing Physics (H557)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-worker-at-a-petrol-station-eb9037b9) · Published by Druglandscape Ltd.